Push-to-talk (Push-To-Talk, PTT) is a mobile voice service for implementing a walkie-talkie (Walkie-talkie) function, and has characteristics that call setup time is short, a channel is occupied only during talking, the channel is monitored only during answering, and a receiving party can answer downlink call information at any time without off-hook. A push to talk over cellular (Push to talk over Cellular, PoC) service is a push-to-talk service based on a packet switch (Packet Switch, PS) domain. Through the PoC service, a user only needs to press one key to conveniently make a personal or group conversation. Compared with a conventional private network cluster communication, with the PoC service, problems of coverage, roaming and inter-communication are solved to a large extent, and therefore, a user group is much greater than a cluster system. Moreover, because an end-to-end voice over Internet protocol (Voice over Internet Protocol, VoIP) technology is adopted, a utilization rate of a network resource can be improved more significantly.
The prior art has at least the following problems: In an existing PoC service, a function related to a dispatcher is not defined and involved, and moreover, a solution to an “emergency call” is not provided.